Biodegradable Sunscreen is a Myth (And you shouldn’t fall for the hype)

Each year over 14 million liters of sunscreen are sold in the United States; enough to fill nearly 6 Olympic sized swimming pools.

How many of those sunscreens, do you think, were biodegradable?

Think of the dozen biodegradable sunscreen brands, eco-friendly sunblock and home-made organic sunblock that you may have heard about.

Well, I have some bad news.

“Biodegradable sunscreen” does not exist.

I know, it’s a bold claim to make but let me ask you:

Have you ever thought of what makes a biodegradable sunscreen eco-friendly?

The answer is a bit more complicated than you might expect. We’ll need to start at the basics and understand how sunscreens protect us from the sun.

Sunscreen basics

Why does a banana wear sunscreen?

Because it peels.

And so do we if we don’t cover up.

The sun is perpetually emitting ultraviolet (UV) radiation with a wavelength between 10 and 400 nm. We’ve identified three wavelength ranges responsible for wrinkles, sunburns and skin cancer.

Ultraviolet-A (315-400 nm) is responsible for the formation of wrinkles and some forms of skin cancer .

Ultraviolet-B (280-315 nm) induces the production of vitamin D in humans but is a leading cause of skin cancer and sunburns.

Ultraviolet-C (100-280 nm) is mostly absorbed by the earth and causes no known harmful effects in humans.

To protect ourselves, we’ve developed sunscreens, which contain compounds that absorb or reflect UV radiation. These are called UV filters.

UV filters can be divided into organic filters, which typically absorb UV radiation and release the energy as heat or as inorganic filters, which reflect UV radiation.

From mud to nanomaterials

Thousands of years ago cavemen likely lathered themselves with mud to protect ourselves from the sun. The ancient Greeks covered themselves up with long robes and used zinc powder. In the 1970’s we smeared thick white paste to keep us from burning. Today, thanks to micronization, modern sunscreens are transparent.

Micronization: to pulverize especially into particles a few micrometers in diameter. Merriam-Webster

The EU Cosmetics Directive (the main EU law on cosmetic safety) has permitted 29 UV filters for sunscreen, of which 27 are organic and two inorganic (titanium dioxide and zinc oxide). For a deeper more in-depth list of organic UV filters check out Skinacea.

Based on their UV filters, sunscreens can be separated into chemical sunscreens and physical sunscreens.

Chemical sunscreens typically only absorb UV-B with a few exceptions.

Physical sunscreens include titanium dioxide and zinc oxide and reflect both UV-A and UV-B radiation.

Physical sunscreen is synonymous with mineral sunscreen. Spray, gel, cream and lotion sunscreens can be of either type depending on the dominant UV filter.

Sunscreens bioaccumulate in the environment

Beach towels can collect sunscreen.

How do sunscreens enter the environment?

Most people would say that they wash off in the water when you go swimming. But what about when you dry yourself afterwards? Have you ever considered the sunscreen that is rubbed off on your towel?

In fact, there are numerous pathways for sunscreens to enter the environment, from the industrial to the individual scale (Giokas et al., 2007).

Factories involved in the industrial production of UV filters discharge their wastewater, which may be treated, or untreated. Individually, we introduce sunscreen into wastewater by washing sunscreens off in the shower, by putting our sunscreen covered towels into the wash or even when we use the toilet (some sunscreens are absorbed into the body). Wastewater eventually makes its way into the environment.

Once in the environment, sunscreen filters begin to do one of two things. They either bioaccumulate in organisms or the UV filter nanoparticles begin to react with the environment.

Good for us ≠ good for the environment

Let’s face it, we need sunscreens but unfortunately the even the best sunblock ingredients come with some significant drawbacks.

In the case of mineral sunscreen filters; titanium dioxide reacts with UV light to produce strong reactive oxygen species (ROS), which can cause significant cellular damage in plant cells (Ma et al., 2010). It also bioaccumulates within many plant species.

Zinc oxide is a common mineral sunscreen ingredient.

Another mineral sunscreen ingredient, zinc oxide, can release free molecules of Zn, which are toxic to the root systems of some plants (Lin and Xing, 2007). Zinc oxide is also toxic to certain bacteria and crustaceans (Heinlaan etal., 2008) and it, like titanium dioxide, readily bioaccumulates and causes toxicity in freshwater fish (Hao et al., 2013).

Quantities of UV filters in the environment vary on the time of day, and body of water, therefore they span quite a range. However, it is not uncommon for levels of organic UV filters to be comparable to PCB (organic pollutants that have been banned for decades now) (Diaz-Cruz et al., 2008).

Groundwater was once thought to be safe from nanoparticles, because we thought nanoparticles were insoluble in natural water, meaning that there should be no bioaccumulation in most organisms. However, with the addition of certain chemical treatments, nanoparticles may easily dissolve into natural waters (Colvin, 2003). Unfortunately, they are often protected by trade secrets and research is tightly controlled.

But all is not lost. New research shows both sides of the coin.

The bioaccumulation of TiO2 nanoparticles does not appear to have short term negative effects on plant cells, despite exposure to levels far above those reported in groundwaters (Foltête et al., 2011) and organic UV-filters , in-light of new evidence regarding coral bleaching, are now banned in many environments.

Furthermore, zinc oxide and titanium dioxide have been supported by the Environmental Working Group, based on current research and look like promising compromises to environmentally friendly sunscreens.

What is a biodegradable sunscreen?

Biodegradable : capable of being broken down especially into innocuous products by the action of living things (such as microorganisms). Merriam-Webster

After what you’ve read, ask yourself:

Is zinc oxide biodegradable?

Is titanium dioxide biodegradable?

The answer is, unsurprisingly, no.

Biodegradable sunscreen does not exist.

Google Scholar, and Scopus (a database for scientific publications) both show 0 publications for the term biodegradable sunscreen.

Most biodegradable sunscreen brands contain zinc oxide and titanium dioxide as the first two ingredients. As you now know, UV filters of mineral sunscreens bioaccumulate in natural organisms rather than being broken down by them because they are simply not biodegradable.

That doesn’t mean that they’re not eco-friendly, only that they’re mislabeled.

Apart from organic-cotton long sleeve shirts, no entirely biodegradable sunscreens are available on the market. Sunscreens have to be worn for the occasion and location. Oxybenzone containing sunscreen should never be applied when you’re swimming in the ocean or near coral reefs, but they may be more acceptable when you’re spending the day in the park.

Environmentally friendly sunscreen ≠ biodegradable sunscreen

The best environmental sunscreen is the one with the least amount ingredients and that will do the least damage to the environment it will be used in.

On a tropical beach, this means using coral-safe sunscreens.

In a freshwater lake a sunscreen with organic UV filters may be better suited.

There is no catch-all solution to sunscreen pollution. But we can improve policies regarding sunscreen use in certain environments.

In Mexican ecoreserves, such as Xel-Há and Xcaret, the use of “non-biodegradable” i.e. sunscreens containing organic UV filters, is banned and only biodegradable sunscreen i.e. mineral sunscreens, are permitted.

In Hawaii there is a movement to ban the sale of sunscreens containing oxybenzone and octinoxate, to help protect coral reefs.

The public can be educated about improving their protection under the sun, by wearing hats, staying covered, going outside when there is less UV radiation and even applying less sunscreen.

Natural sunscreen and organic sunscreen: the truth

I’m sure you’ve seen the headlines on other blogs before:

“Home-made UV-blocking natural sunscreen.”

“Make your own organic sunscreen.”

Don’t be fooled by marketing labels such as natural sunscreen or organic sunscreen. The former only implies there are no artificial ingredients (mineral sunscreens are already natural), while the later signifies that the sunscreen is pesticide-free (as all sunscreen should already be…). Other sunscreen brands may say they’re “non-nano” but there is no regulation on that claim.

Instead of the sun turning you bright beet root red, you’d have to do it yourself. The authors did note that these strong colors could be mitigated by mixing the natural sunscreen ingredients with mineral sunscreen or other UV filters.

Raspberry seed oil appears to have UV filtering capabilities; however, it should not be used on its own as a sunscreen. Combining raspberry oil with nanostructured lipid carriers (nano-sized fats that encapsulate the oil to better spread it), led to a SPF of only 17.3 (Niculae et al. 2014).

The future of biodegradable sunblock

Biodegradable sunscreen on the market currently does not exist. However, there is hope for the future by combining natural ingredients with minuscule amounts of organic/inorganic UV filters. These would lead to less UV filters entering the environment, and less bioaccumulation.

Natural and biodegradable sunscreen, which will protect from UV-A and UV-B.

What can you do?

Be knowledgeable and vigilant.

Read the ingredients on your sunscreens and make an active decision on your next purchase.

Spread your knowledge to others, let them know about how sunscreens work. Push companies to reduce the amounts of non-biodegradable UV filters and research more into environmentally friendly sunscreen. Already this push has lead to increased interest in eco-friendly products, and we’ve written a lengthy article on biodegradable shampoo for those interested.